The task is challenging. We need storage technology for really large amounts of energy. The sheer size of the amount of energy to be stored is not the only problem. The storage facilities would also have to be affordable and have a high efficiency rating (over 85%).
You may have noticed that there is currently an “enormous” increase in investment in electricity storage, whether through the installation of batteries for small solar systems or medium-sized industrial facilities. By “enormous,” these reports meant an increase of approximately 500 GWh in 2025 (in germany). However, we need a storage capacity of 20,000–40,000 GWh for a stable power supply for a country of in a size of germany. An additional 200,000 GWh is needed to provide heating in winter (for a country at a similiar latitude and size like germany).
There is no technology on the market yet that could handle this task. Only concepts of varying degrees of poor quality.